Presence Of Iodosobenzene Research Articles

Green Approach for the Synthesis of a New Class of Diamidomethane‐linked Benzazolyl Pyrazoles and Evaluation as Antifungals

A new class of diamidomethane‐linked benzoxazolyl pyrazoles, benzothiazolyl pyrazoles, and benzimidazolyl pyrazoles were synthesized from the synthetic intermediates N‐benzazolylcarbamoylmethylcinnamides adopting environmentally benign methods. In fact, nitrile imine was generated from araldehyde phenylhydrazone in the presence of iodosobenzene and cetyltrimethylammonium bromide followed by oxidation with iodine in dimethylsulfoxide. The structures of compounds were characterized by IR, 1H NMR, 13C NMR, and mass spectra. The title compounds were also evaluated for their antifungal activity. Amongst all the tested compounds benzimidazolyl pyrazolyl carboxamides (13a and 13b) were found to be potential antifungal agents.

Oxidative Cyclization of β-Aminoacrylamides Mediated by PhIO: Chemoselective Synthesis of Isoxazoles and 2 H-Azirines.

Cyclization of a variety of β-aminoacrylamides in the presence of iodosobenzene (PhIO) is described. This process features mild reaction conditions, simple execution, and high chemoselectivity and thereby provides an efficient protocol for the divergent synthesis of substituted isoxazoles and 2 H-azirines via switchable N-O and N-C bond formation controlled by simply varying the β-substituent R3 of the readily available substrates.

Iodosobenzene-Mediated α-Acyloxylation of 1,3-Dicarbonyl Compounds with Carboxylic Acids and Insight into the Reaction Mechanism.

A highly efficient direct α-acyloxylation of 1,3-dicarbonyl compounds with carboxylic acids mediated by hypervalent iodine reagent is presented. Treatment of a variety of 1,3-dicarbonyl compounds with carboxylic acids in the presence of iodosobenzene provides the corresponding α-acyloxylated products in good to excellent yields. The mechanistic investigation by means of NMR spectroscopy reveals that the in situ-generated phenyliodine biscarboxylate proves to be the key intermediate for the α-acyloxylation, and the loading sequence of reactants and oxidant is crucial for the generation of the active species. The mild reaction conditions, wide substrate scope, short reaction time, good yields, high chemoselectivity, excellent functional group tolerance, and metal catalyst-free conversion make this acyloxylation a significant synthetic protocol.

Green approach for the synthesis of thiophenyl pyrazoles and isoxazoles by adopting 1,3-dipolar cycloaddition methodology and their antimicrobial activity

A variety of N-((1,3-diphenyl-5-aryl-1H-pyrazol-4-yl)sulfonyl)thiophene-2-carboxamides (7) and N-((5-aryl-3-phenylisoxazol-4-yl)sulfonyl)thiophene-2-carboxamides (8) were prepared from (E)-N-(arylethenesulfonyl)thiophene-2-carboxamides (4) adopting 1,3-dipolar cycloaddition of nitrile imines and nitrile oxides generated from araldehyde phenylhydrazones and araldoximes in the presence of iodosobenzene and CTAB followed by oxidation with I2 in DMSO. The compounds 4f, 7e, 7f, 8e and 8f showed potential antibacterial activity against B. subtilis whereas 8e and 8f exhibited potential antifungal activity against A. niger.

An Inverted and More Oxidizing Isomer of [FeIV(O)(tmc)(NCCH3)]2+

Oxoferryl gymnastics: The oxo and CH3CN ligands in 1-NCCH3 can swap positions in the presence of iodosobenzene and tetrafluoroborate anion leading to the generation of a more reactive isomer 2. This conversion is proposed to take place via an activated FeIV unit (1 a) or a transient dioxoiron(VI) species (1 b).

Comparison of Activity of Immobilised and Soluble Metalloporphyrins by NO Release of Oximes by Chemiluminescence

The ongoing interest in very efficient systems for the imitation of cytochrome P-450-dependent monooxygenase reactions, consisting of metalloporphyrin and oxygen donor, prompted us to develop a method to compare the catalytic activity of soluble metalloporphyrins with those which have been immobilised on different silica surfaces. In this article, we describe a method which allows direct comparison between the catalytic activities of soluble and immobilised metalloporphyrins by measuring the NO release of cyclohexanone oxime. We observed that all metalloporphyrins are able to enhance the NO release of cyclohexanone oxime in the presence of iodosobenzene as oxygen donor. In case of cationic metalloporphyrins, no difference in the catalytic activity was determined. In contrast, for perfluorinated metalloporphyrins we ascertained a major loss of activity after immobilisation. These results led us to the assumption that it is not easy to compare quantitative results of NO releases if soluble and immobilised metalloporphyrins were used.

Spectroscopy, electrochemistry and catalytic properties of ruthenium II complexes containing the tetradentate Schiff base ligand N, N′-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane

The trans-dichlororuthenium II complex with the tetradentate Schiff base ligand, N, N′-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane, has been synthesized and characterized. In contact with water, it converts into the diaqua complex, leading to pronounced changes in the electronic and electrochemical behavior. This species exhibits remarkable activity in the epoxidation of cyclohexene in the presence of iodosobenzene (PhIO).

Ruthenium(II) complexes with 2,6-pyridyl-diimine ligands: synthesis, characterization and catalytic activity in epoxidation reactions

Reaction of [RuCl 2( p-cymene)] 2 with the tridentate N- N′- N ligands, 2,6-pyridyl-diimines, led to substitution of p-cymene. The resulting complexes, believed to be coordinatively unsaturated, exhibit efficient activity for the epoxidation of cyclohexene in the presence of iodosobenzene (PhIO): the complexes formed initially take up donor molecules such as acetonitrile to achieve hexacoordination. The molecular structure for one of these, (acetonitrile){2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine}dichlororuthenium(II), 2, has been determined by X-ray diffraction. The immediate coordination sphere is a distorted octahedron with trans chloride atoms and a short Ru–N(py) (1.906 Å) bond.

Cyclodehydrogenation of 2′‐hydroxychalcones with hypervalent iodine reagent: A new synthesis of flavones

AbstractA new synthesis of chrysin (1) and luteolin (4) was accomplished by the cyclodehydrogenation of the appropriately substituted 2′‐hydroxychalcones 21 and 22 in the presence of iodosobenzene diacetate/potassium hydroxide in methanol. The scope and limitation of this transformation is discussed.

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: XXXI. Über ein- und zweikernige halogenorhenium(V)-komplexe: synthesen und strukturen

The dinuclear oxorhenium complex of composition [(η 5-C 5Me 5)ReO 2] 2 ( 1) is subject to clean cleavage upon treatment with aqueous hydrogen fluoride, chloride, and bromide, thus yielding the mononuclear halfsandwich complexes (η 5-C 5Me 5)ReOX 2 (X  F, 2a; Cl, 2b; Br, 2c). The multistep mechanism of these reactions starts off with O-protonation of the Re 2O 2 core as demonstrated by an independent synthesis of the isolable ionic intermediate [(η 5-C 5Me 5) 2Re 2(μ-OH) 2O 2][BF 4] 2 ( 5). A low-yield side product of the reaction of 1 with aqueous hydrochloric acid is the dinuclear complex [(η 5-C 5Me 5)Re(μ-O)Cl 2] 2 ( 4). The dichloro complex 2b, is easily prepared by treating (η 5-C 5Me 5)ReO 3 with germanium dichloride (dioxane complex; GeCl 2 · C 4H 8O 2). The preparation of the diiodo derivative (η 5-C 5Me 5)ReOI 2 2d) has been achieved by photolysis of (η 5-C 5Me 5)Re(CO) 3 in the presence of iodosobenzene. The molecular and crystal structure of (η 5-C 5Me 5)ReOCl 2 ( 2b) has been determined by single crystal X-ray diffraction techniques. Action of trimethylaluminum upon the dibromorhenium(V) complex 2c yields the dimethyl derivatives (η 5-C 5Me 5)ReO(CH 3) 2 and (η 5-C 5Me 5)ReBr 2(CH 3) 2 ( 6).

High-valent oxo complexes of osmium as selective oxidants for cyclohexene oxidation. Complexation of the bisamide tetradentate ligand bpb to osmium and the X-ray structure of trans-[osIII(bpb)(PPh3)Cl][bpbH2=N,N′-bis(2′-pyridine-carboxamide)-1,2-benzene

The reaction of N,N′-bis(2′-pyridinecarboxamide)-1,2-benzene (bpbH2) with K2[OsO2(OH)4] yielded trans-[OsVI(bpbH2)O2]2+ which in turn gave trans-[OsIII(bpb)(PPh3)Cl] upon treatment with PPh3; the OsIII complex has been characterized by X-ray crystallography and found to catalyse the epoxidation of cyclohexene in the presence of iodosobenzene.

Chemical mechanisms for cytochrome P-450 oxidation: spectral and catalytic properties of a manganese-substituted protein.

Bacterial cytochrome P-450 induced by camphor (P-450cam) is reconstituted with manganese-protoporphyrin IX, yielding an enzyme that displays unique spectral properties relative to previously characterized manganese-porphyrin systems. The nitric oxide complex of the manganese(II)-protein shows a hyper-metalloporphyrin spectrum suggestive of thiolate ligation to the porphyrin-bound manganese ion. In the presence of iodosobenzene as a source of active oxygen, manganese-substituted cytochrome P-450cam serves as a catalyst for the epoxidation of an enzyme-bound olefin substrate. This reactivity proceeds through a spectrally detectable intermediate that resembles the manganese(V)-oxo complexes that have been well documented with model systems employing artificial manganese-metalloporphyrins in organic solution. Interestingly, manganese-substituted cytochrome-P-450cam shows no hydroxylation activity either in the reconstituted camphor hydroxylase system with pyridine nucleotide or in the presence of iodosobenzene and the Mn(III) form of the protein.

Mechanisms of hydroxylation by cytochrome P-450: Exchange of iron-oxygen intermediates with water

Highly-purified rat liver microsomal cytochrome P-450 converted cyclohexane to cyclohexanol in the presence of iodosobenzene. Oxygen from 18O-iodosobenzene was not incorporated into cyclohexanol but oxygen from H 2 18O was readily incorporated. Cytochrome P-450 catalyzed the facile exchange of oxygen between iodosobenzene and water but neither cytochrome P-420 nor the apoenzyme did. Under these conditions cytochrome P-450 readily incorporated oxygen from 18O 2 into cyclohexanol in the presence of NADPH-cytochrome P-450 reductase and NADPH. The results are interpreted in a mechanism in which cytochrome P-450 forms a common hydroxylating species in the presence of iodosobenzene or O 2 plus NADPH.

Cytochrome P450 as an oxene transferase

In the presence of iodosobenzene, liver microsomes catalyze the O-dealkylation of 7-ethoxycoumarin. The reaction proceeds in the absence of NADPH and O 2 and is dependent on cytochrome P450. The results indicate that cytochrome P450 acts as an oxene transferase probably involving [FeO] 3+ as the transient intermediate of active oxygen.